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.\" $OpenBSD: ASN1_BIT_STRING_set.3,v 1.1 2021/11/15 16:18:36 schwarze Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: November 15 2021 $
.Dt ASN1_BIT_STRING_SET 3
.Os
.Sh NAME
.Nm ASN1_BIT_STRING_set ,
.Nm ASN1_BIT_STRING_set_bit ,
.Nm ASN1_BIT_STRING_get_bit ,
.Nm ASN1_BIT_STRING_check
.Nd ASN.1 BIT STRING accessors
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft int
.Fo ASN1_BIT_STRING_set
.Fa "ASN1_BIT_STRING *bitstr"
.Fa "unsigned char *data"
.Fa "int len"
.Fc
.Ft int
.Fo ASN1_BIT_STRING_set_bit
.Fa "ASN1_BIT_STRING *bitstr"
.Fa "int bitnumber"
.Fa "int set"
.Fc
.Ft int
.Fo ASN1_BIT_STRING_get_bit
.Fa "ASN1_BIT_STRING *bitstr"
.Fa "int bitnumber"
.Fc
.Ft int
.Fo ASN1_BIT_STRING_check
.Fa "ASN1_BIT_STRING *bitstr"
.Fa "const unsigned char *goodbits"
.Fa "int goodbits_len"
.Fc
.Sh DESCRIPTION
.Fn ASN1_BIT_STRING_set
sets the length attribute of
.Fa bitstr
to
.Fa len
and copies that number of bytes from
.Fa data
into
.Fa bitstr ,
overwriting any previous data, by merely calling
.Xr ASN1_STRING_set 3 .
This function does no validation whatsoever.
In particular, it neither checks that
.Fa bitstr
is actually of the type
.Dv V_ASN1_BIT_STRING
nor, even if it is, that the
.Fa data
and
.Fa len
arguments make sense for this particular bit string.
.Pp
If the
.Fa set
argument is non-zero,
.Fn ASN1_BIT_STRING_set_bit
sets the bit with the given
.Fa bitnumber
in the
.Fa bitstr ;
otherwise, it clears that bit.
A
.Fa bitnumber
of 0 addresses the most significant bit in the first data byte of
.Fa bitstr ,
7 the least significant bit in the same byte,
8 the most significant bit in the second data byte, and so on.
.Pp
If setting a bit is requested beyond the last existing data byte,
additional bytes are added to the
.Fa bitstr
as needed.
After clearing a bit, any trailing NUL bytes are removed from the
.Fa bitstr .
.Pp
.Fn ASN1_BIT_STRING_get_bit
checks that the bit with the given
.Fa bitnumber
is set in
.Fa bitstr .
.Pp
.Fn ASN1_BIT_STRING_check
checks that all bits set in
.Fa bitstr
are also set in
.Fa goodbits .
Expressed symbolically, it evaluates:
.Pp
.D1 Po Fa bitstr No & Pf \(ti Fa goodbits Pc == 0
.Pp
The buffer
.Fa goodbits
is expected to contain
.Fa goodbits_len
bytes.
.Sh RETURN VALUES
.Fn ASN1_BIT_STRING_set
returns 1 on success or 0 if memory allocation fails or if
.Fa data
is
.Dv NULL
and
.Fa len
is \-1 in the same call.
.Pp
.Fn ASN1_BIT_STRING_set_bit
returns 1 on success or 0 if
.Fa bitstr
is
.Dv NULL
or if memory allocation fails.
.Pp
.Fn ASN1_BIT_STRING_get_bit
returns 1 if the bit with the given
.Fa bitnumber
is set in the
.Fa bitstr
or 0 if
.Fa bitstr
is
.Dv NULL ,
if
.Fa bitnumber
points beyond the last data byte in
.Fa bitstr ,
or if the requested bit is not set.
.Pp
.Fn ASN1_BIT_STRING_check
returns 0
if at least one bit is set in
.Fa bitstr
that is not set in
.Fa goodbits ,
or 1 otherwise.
In particular, it returns 1 if
.Fa bitstr
is
.Dv NULL
or if no bit is set in
.Fa bitstr .
.Sh SEE ALSO
.Xr ASN1_BIT_STRING_new 3 ,
.Xr ASN1_STRING_set 3 ,
.Xr d2i_ASN1_BIT_STRING 3
.Sh HISTORY
.Fn ASN1_BIT_STRING_set
first appeared in SSLeay 0.6.5.
.Fn ASN1_BIT_STRING_set_bit
and
.Fn ASN1_BIT_STRING_get_bit
first appeared in SSLeay 0.9.0.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn ASN1_BIT_STRING_check
first appeared in OpenSSL 1.0.0 and has have been available since
.Ox 4.9 .
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